Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON):

Solution:
H, W = map(int, raw_input().split())
s = []
w = 0
for i in range(H):
  l = raw_input()
  s.append(l)
  w += l.count(".")
C = []
for i in range(H):
  C.append([10000]*W)
C[0][0]=1
q = [(0,0)]
while q:
  i, j = q.pop(0)
  for d in [(+1,0),(-1,0),(0,+1),(0,-1)]:
    ni = i+d[0]
    nj = j+d[1]
    if 0<=ni<H and 0<=nj<W and s[ni][nj]=="." and C[i][j]+1<C[ni][nj]:
      C[ni][nj] = C[i][j]+1
      q.append((ni,nj))
if C[H-1][W-1]==10000:
  print -1
else:
  print w-C[H-1][W-1]